Apparatus and method for grooving a board-like material, a grooving tool therefor and a structure made by the method

ABSTRACT

Apparatus and method for forming V-shaped grooves in a board material including a grooving tool having a V-shaped leading cutting edge with a preselected included angle for cutting a V-shaped groove to a preselected depth in the board material, means for producing relative movement of said grooving tool and said board material to cut the V-shaped groove in said board material, guide means for inhibiting nonlinear relative movement of said grooving tool and said board material to cause a straight groove to be cut in said board. The board material thus grooved may be folded to form structures for use as boxes and in certain furniture applications.

BACKGROUND OF THE INVENTION

The invention relates to forming V-shaped grooves in board materialssuch as paperboard, chipboard and particle board and more particularlyto a method and apparatus for groove folding such board materials toform structures, such as boxes.

In a desire to lower cost by using more plentiful materials, box makersand furniture makers are turning away from wood and the like in favor ofcomposite board materials for forming both decorative and structuralpanels. It has been customary, in forming the four sides of a wooden boxto join four panels together at their edges using a joint such as a buttjoint or a dovetail joint. However, butt joints are relatively weak anddovetail joints involve manipulations which are detailed and thereforeexpensive. Dovetail joints require cutting or punching notches andprojections in both ends of all boards, applying glue, fitting theinterlocking notches and projections of the four panels together to formthe sides of the box and blocking the four-sided structure in arectangular shape until the glue sets. A further finishing operation totrim the projections may also be required. In addition to the cost ofsuch an operation, the step of cutting or punching the notches andprojections produces a large quantity of dust and small scrap materialwhich must be collected and disposed of.

Boxes have also been made by routing grooves in flake board with arotating routing tool. Flake board is a dense, hard material made ofwood shavings and chips bonded into a board. Routing the flake boardproduces large quantities of dust which may present a health hazard tothose working with this process.

Paper boxes or box-like structures of light weight paperboard or ofcorrugated paperboard may be fabricated by creasing a single piece ofthe board and folding the board along the crease lines which define thebox corners. The fold or crease lines are produced by cutting partiallythrough the material or by compressing grooves in the material. However,compression grooving is not effective to define corners on allthicknesses of solid paperboard or particle board. As board thicknessincreases, the stiffness of the board and its limited receptivity tocreasing causes the board fibers at the outer radii of the corners tocrack and break due to tension in the fibers. Even at lesserthicknesses, corners formed by compression grooving and folding areoften unsatisfactory since they are rounded and not sharply defined.

In order to bend thicker paperboard to produce reasonably squarecorners, a process known as step grooving has been used. Step groovingconsists of removing a first relatively wide and shallow rectangularstrip of material and then removing a relatively narrow and deeprectangular strip of material from the center of the wide and shallowgroove. The paperboard is then folded along the line thus defined.

However, step grooving has several disadvantages. Step grooving requirestwo grooves and produces a large amount of scrap. Also, the resultinggrooves are generally ragged since shreds of paper fibers are attachedto the walls of the grooves. In addition, the opposed edges of the stepgrooves abut in an irregular fashion when they are folded to form acorner. Furthermore, the outside edges of the corners so formed are notsharply defined.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art byproviding a device which slides a V-shaped groove in thick boardmaterial. The V-shaped groove is cut at a predetermined included angleand is cut so that the sides of the V-shaped groove are smooth. Thus,the opposing sides of the V-shaped groove form a strong close fittingcorner when folded together. By controlling the depth of the V-shapedgroove in the board, the corner may be sharply defined to avoid therounded corners obtained with many prior art methods.

The present invention also reduces the health hazards associated withthe dust formed during prior art processes, since each V-shaped grooveof the present invention is formed by removing a single V-shaped filletof board material which is easily disposed of. Furthermore, the presentinvention is more simple than prior art processes since it replaces themultiple grooves of the prior art with a single groove. In addition, bypreselecting the included angle of the V-shaped groove, strong box-likestructures having any number of sides and shapes may be formed. Thesestructures may be used not only for packaging purposes but also for manyfurniture applications, such as, cabinets and tables. The structures maybe covered with a decorative laminate to give them an attractiveappearance.

According to one aspect of the invention, an apparatus is provided forforming a groove in a sheet of board material. The apparatus comprises agrooving tool which is provided with a V-shaped leading cutting edgehaving a preselected included angle to cut a V-shaped groove to aselected depth in the board material. The board material is guided andmaintained firmly against a support by a hold down and the V-shapedgroove is formed by driving the board material relative to the groovingtool to cut the V-shaped groove in the board material. Optionally, thegrooving tool is mounted on the hold down and is adjustable to vary thedepth of the V-shaped groove formed.

According to a feature of the invention, a method is provided forforming a groove in a sheet of board material. The groove is formed byguiding and advancing a sheet of board material relative to the V-shapedcutting edge of the grooving tool and cutting a V-shaped groove having apreselected included angle to a preselected depth in the board material.After the board material is grooved, box like structures may be formedby folding the board material along the grooves.

In order to insure a properly formed groove, the method may also includesupporting the sheet on a support and maintaining the sheet in firmengagement with the grooving tool as the sheet advances relative to thegrooving tool.

According to a further feature of the invention, a grooving tool isprovided for forming a V-shaped groove in board material. The toolincludes a body which is provided with a V-shaped cutting edge having apreselected angle. In one preferred embodiment, the tool includes a bodyhaving a shank portion and a shoe portion, the shank portion beingadapted for fastening the grooving tool to a support and, the shoeportion preferably including a V-shaped bottom which is adapted forfitting in the V-shaped grooves. At the end of the shoe portion aV-shaped leading cutting edge having a preselected included angle isformed. Preferably, the inner contour of the shoe portion is curved todirect the V-shaped fillet cut from the groove away from the sheet.

The above and other advantages of the invention will become apparentfrom the following description of the preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a grooving apparatus according to anembodiment of the present invention.

FIG. 2 is a side sectional view of the grooving apparatus of FIG. 1taken along II--II of FIG. 1 showing an embodiment of a grooving tooland hold down according to the invention.

FIG. 3 is a back sectional view of the hold down and grooving tool takenalong III--III of FIG. 2 illustrating a mechanism for urging the wheelof the hold down against the board being grooved.

FIG. 4 is a front sectional view of the hold down and grooving tooltaken along IV--IV of FIG. 2 showing the grooving tool cutting a groovein the board material.

FIG. 5 is a perspective view of a box, partially assembled, madeaccording to an embodiment of the invention.

FIG. 6 is a plan view of a sheet of board material used with the presentinvention.

FIG. 7 is a plan view of another board sheet utilized with theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a grooving machine 10 according to an embodiment ofthe invention. Grooving machine 10 includes a base 12 and first andsecond side walls 14 and 16. A heavy roller 18, preferably of steel, isjournalled in side walls 14 and 16 to rotate in the direction shown byan arrow 20. A superstructure 22 mounted between side walls 14 and 16and above roller 18 supports a plurality of hold-downs 24 in apredetermined relationship to roller 18 and side walls 14 and 16.Hold-downs 24 may optionally be laterally displaceable using, forexample, a dovetail 26 which, although shown in cross section in FIG. 2for clarity, extends substantially the full width below superstructure22. Thus, hold-downs 24 can be laterally positioned anywhere across thewidth of the grooving machine between side walls 14 and 16. Hold-downs24 each include a hold-down wheel 66. A grooving tool 28 is affixed tocertain hold-downs 24. A board 30 to be grooved is supported on aplatform 76 which is positioned tangential to roller 18. Roller 18 whichrotates in the direction of arrow 20 is belt driven through a pulley 38coaxial with roller 18. A guard 40 prevents accidental contact withpulley 38 or the belt.

Board 30 is fed and pinched between wheels 66 and roller 18 and is thusforceably moved in the direction of an arrow 32. As board 30 is advancedrelative to grooving tools 28, the grooving tools 28 cut V-shapedfillets 34 from the surface of board 30 forming V-shaped grooves 36athrough 36e. Although hold-downs 24 are shown in association withgrooving tools 28, additional hold-downs 24' may be employed to securelypinch board 30 between hold-down wheel 66 and roller 18. In a preferredembodiment, from 3 to 6 additional hold-downs 24' are disposed betweenthose shown. If insufficient hold-downs are provided, board 30 tends toturn or snake while being grooved resulting in curved V-shaped grooves36.

The rotating mass of roller 18 smoothly drives board 30 through theapparatus. Although it is normal to drive such a roller with a motor of1 or 2 horsepower, improved operation is achieved with higher power. Ina preferred embodiment, a roller weighing about 700 pounds is driven bya 7.5 horsepower motor.

FIGS. 2, 3 and 4 illustrate a hold-down 24 maintaining the board 30 infirm contact with the roller 18 and maintaining the board 30 in firmcontact with grooving tool 28 as the board 30 is driven past groovingtool 28.

Referring to the top of FIG. 2, dovetail 26 is attached tosuperstructure 22 using a number of countersunk screws 42 (one of whichis shown in dashed lines). A slot 44 in hold-down 24 includes a beveledabutment surface 46 which is operative to abut a matching beveledsurface 48 on dovetail 26. A holding member such as, for example, arectangular plate 47 is held by two pins 49 (one of which is shown)which pass through plate 47 and are held fast in hold-down 24. Plate 47is movable in the direction of arrow 51 on pins 49. A screw 50 issuitably threaded through hold-down 24 and has its ends in stabilizingcontact with plate 47 forcing the plate into abument with beveled tailsurface 52 of dovetail 26. A forward flat upper surface 54 and a rearflat upper surface 56 of hold-down 24 are drawn upward into stabilizingcontact with a flat lower surface 58 of superstructure 22 by forcingtogether the beveled abutment surface 46 and beveled surface 48 tosecurely hold and stabilize hold-down 24 against superstructure 22.

In the lower left hand portion of FIG. 2, a pivoted member 60 within acavity 62 in hold-down 24 is pivoted at an axis 64. Hold-down wheel 66is a bearing which is rotatable on an axle 68 suitably screwed intopivoted member 60. A compression coil spring 70, in the right handportion of FIG. 2 and also shown in FIG. 3, is biased between the bodyof hold-down 24 and the trailing end of pivoted member 60 to urgepivoted member 60 in the clockwise direction of FIG. 2 about axis 64 andthus to urge hold down wheel 66 firmly against board 30. A limit screw72 adjustable by a limit nut 74 passes through the helix of compressioncoil spring 70 to limit the outward travel of pivoted member 60 underthe urging of compression coil spring 70.

Hold-down 24 may be constructed without a spring-biased pivoted member.Satisfactory operation has been obtained using a rigid hold-down 24. Theeffect of a rigid hold-down may be achieved by fully tightening limitscrew 72 and nut 74 or by fabricating a solid hold-down 24 (not shown)in which the hold-down wheel 66 is rotatably affixed to the bodythereof.

Referring also to FIG. 1, a platform or table 76 is provided at therun-in side of grooving machine 10 to support and feed board 30 to thenip between hold-down wheel 66 and roller 18. A suitable platform ortable (not shown) may also be provided at the run-out side of theapparatus to receive board 30 after the grooving operation is completed.

As illustrated in FIGS. 2 and 4, grooving tool 28 has a shank portion 78and a shoe portion 80. Shank portion 78 is substantially rectangular forclose abutment to its support member which may be, for example,hold-down 24 (FIG. 4). A plurality of capscrews 82, passing throughslotted openings 84, are threaded into threaded holes 85 (FIG. 3) inhold-down 24 to adjustably clamp grooving tool 28 against hold-down 24.As can be seen in FIG. 2, the range of adjustment of grooving tool 28permits the depth of groove 36 to be adjusted to a preselected valuewhich may be shallow or in the extreme, fully through board 30 wherebyboard 30 is severed. Thus, dimension d, measured from the bottom ofgroove 36 to the opposite surface of board 30, is controllable byloosening capscrews 82 and sliding grooving tool 28 upward and downwardguided by slotted openings 84.

Shoe portion 80 has a V-shaped bottom 86 having a substantially straightlower edge 87 and having an included angle 88 (FIG. 4) substantiallyequal to the included angle of fillet 34 and groove 36. V-shaped bottom86 has a V-shaped sharpened leading or cutting edge 92 disposed to cutor slice board 30 when it is moved in the transport direction 32 (FIG.2). The opposing sides of V-shaped bottom 86 are substantially coplanarwith opposing sides of V-shaped edge 92.

The grooving tool 28 is provided with an inner contour 94, shown dashedin FIG. 2 and solid in FIG. 4, which is curved to smoothly lift theV-shaped fillet 34 from the position at which it is severed by cuttingedge 92 to the discharge position shown.

To resist dulling by the abrasive nature of, for example, particleboard, at least cutting edge 92 may be made of hardened material such ashardened tool steel. In the preferred embodiment, the entire groovingtool 28 is hardened tool steel.

Bottom edge 87 of V-shaped bottom 86 may ride tightly in V-shaped groove36 or it may be tilted upward a small angle, such as angle 96. Angle 96is preferably as small as two or ten degrees, inclusive but satisfactoryoperation has been achieved with angle 96 as large as 20 degrees. Bykeeping angle 96 small, cutting edges 92 perform a shaving action onboard 30 to produce a smooth clean V-shaped groove 36. Best operation isachieved with angle 96 about 7 degrees.

The permissible values of included angle 88 of cutting edge 92 dependupon the thickness d from the bottom of V-shaped groove 36 to theoutside surface of board 30. If d is very small (approaching zero),angle 88 may approach 90 degrees to form a square corner. As thickness dincreases somewhat, angle 88 must increase to provide clearance forfibers pressed into the inner radius of the bend. An angle as large as95 degrees has given satisfactory results for producing square cornerswith best results being obtained in the range of 91.5 to 93.5 degrees,inclusive. However, if d is permitted to grow too large, the cornersformed may be rounded.

In use, hold-downs 24 and attached grooving tools 28 having apreselected angle 88 are secured at desired positions along the lengthof dovetail 26. Additional hold-downs 24' may be provided to improvestability. In addition to maintaining the grooving tool 28 in firmengagement with board 30 while cutting the grooves 36, the hold-downs 24guide the board 30 to prevent the board from turning as the grooves 36are formed.

The number of grooving tools 28 utilized and the spacing betweengrooving tools 28 is dependent on the number of folds and the shape ofthe structure desired. In FIG. 1, five grooving tools 28 are illustratedand are positioned such that the distances between adjacent groovingtools are the same.

Before feeding board 30 between roller 18 and hold-downs 24, thehold-downs 24 and the grooving tool 28 are adjusted so that the grooves36 are formed properly in the board 30. In order to adjust the tensionof hold-down wheel 66 against the board 30, limit screw 72 is adjusted.By tightening limit screw 72, the coil spring 70 of hold-down 24 iscompressed resulting in more tension between hold-down wheel 66 androller 18. When limit screw 72 is loosened, spring 79 relaxes andtension between wheel 66 and roller 18 is decreased. Optimally, wheel 66exerts just enough tension on board 30 to prevent the board from turningas it passes between the roller 18 and wheel 66. However, excess tensionshould be avoided to prevent excessive drag on board 30.

The depth to which grooving tool 28 cuts is adjusted by looseningcapscrews 82 permitting grooving tool 28 to slide along the length ofslotted openings 84 and move cutting edge 92 either closer to or awayfrom roller 18. Capscrews 92 are tightened in threaded holes 85 to clampgrooving tool 28 against hold-down 24 when the desired adjustment ismade. The cutting edge 92 may be brought close enough to roller 18 suchthat the cutting edge cuts entirely through board 30 and board 30 issevered. In FIG. 1, the two grooving tools 28 forming grooves 36a and36e are adjusted to cut completely through board 30. The three interiorgrooving tools 28 forming grooves 36b, 36c and 36d are adjusted to cutto a preselected depth which is less than the thickness of the board.

After the adjustments are made, the grooving machine 10 is operated byrotating roller 18 which is belt driven through pulley 38. As roller 18rotates in the direction of arrow 20, board 30, which is supported onplatform 76, is fed between hold-down wheel 66 and roller 18. The board30 is driven in the direction of arrow 32 past grooving tools 28. Fivegrooves 36a,b,c,d and e are formed. Grooves 36b,c and d are V-shapedgrooves and grooves 36a and 36e, which are cut entirely through board30, form beveled ends 100.

The board 30 with the grooves 36 formed therein is folded along grooves36b, c and d until the sides of each groove meet to produce three of thefour corners of rectangular structure 98 (FIG. 5). The beveled ends 100are brought together and secured to form the fourth corner of therectangular structure.

FIG. 5 illustrates such a rectangular structure or box 98 partiallyassembled, of grooved board 30. Three V-shaped grooves 36, when foldeduntil their sides substantially meet, produce three of the four cornersof rectangular structure 98. The remaining beveled ends 100 of structure98 are mated as shown by the dashed line to form the fourth corner ofthe structure. Referring also to FIG. 1, ends 100 are formed by cuttingV-shaped grooves 36a and 36e completely through board 30 to leave thesubstantially 45 degree beveled ends 100. Thus, when the box structureis closed, the beveled ends 100 closely abut each other to complete thestructure. For strength, glue may be coated on the beveled surfaces ofgrooves 36 and ends 100 before folding into the shape shown in FIG. 5whereby the facing surfaces are bonded together. Other means of securingthe beveled ends of box 98 together such as, for example, metalfasteners or flexible tapes, are included within the scope of thepresent invention.

FIG. 6 illustrates an S-shaped board 101 used in making a four-sided boxhaving a top and bottom. By cutting vertical grooves 102a,b,c and d, andhorizontal grooves 104a,b,c,d,e, five panels A,B,C,D and E are formed.At points along the outer edge of S-shaped board 101, where grooves 102and 104 are not formed between two adjacent panels, the grooves 102 and104 bevel the circumference of S-shaped board 101 similar to beveledends 100 formed on board 30.

In use, the S-shaped board 101 is driven past four grooving tools 28 ofgrooving machine 10 to form grooves 102a to d. The board 101 is thenrotated 90 degrees and driven past five grooving tools of groovingmachine 10 to form grooves 104a to e and panels A to E. By foldingpanels B,C,D and E along grooves 104b,c, and d to bring outer edges 110aand 110b together, a four-sided structure is formed. Edges 110a and 110bmay be secured in any convenient manner, such as with a metal fastener.Panels A and F form the top and bottom of the structure. Groove 102cbetween panels A and B forms a hinge 113a between panels A and B. Groove102b between panels E and F forms a hinge 112b between panels E and F.When panels A and F are folded along hinges 113a and b to form the topand bottom of the structure, the beveled circumference of the S-shapedboard 101 permits a tight fit between panels A and F and the structureformed by panels B,C,D and E. The three unattached sides of panels A andF may be attached to the structure formed by panels B,C,D and E in anyconvenient manner. In order to form a box which can be opened andclosed, the three unattached sides of either panel A or panel F may beleft unattached or one of the free sides may be secured to either panelB,C,D or E with a conventional latching device.

Referring to FIG. 7, another board construction used for making astructure is illustrated. A rectangular board 105 is formed having fivegrooves 106a,b,c,d and e. Grooves 106a and c at board edges 114a and bbevel the edges 114a and b in a manner like beveled edges 100 of board30. Board edges 114c and d are not beveled. The board 105 is providedwith two additional grooves 108a and b which are at 90 degrees togrooves 106. The portion of grooves 106b,c and d between groove 108a andboard edge 114c and between groove 108b and edge 114d, passes throughboard 105 and forms six cuts 112 in the board 105. Thus, 12 panels, Hthrough S are formed in board 105. Panels L, M, N and O may be foldedalong grooves 106b,c and d to bring edges 114a and 114b together to forma four-sided structure. Panels H, I, J and K and panels P, Q, R and Smay be folded along grooves 108a and 108b, respectively to form the topand bottom of the structure.

In use, board 105 is driven past five grooving tools 28 of machine 10 toform grooves 106a,b,c,d and e. Cuts 112 may be formed, prior to or aftergrooves 106a to e are formed, by any conventional slicing method.Alternatively, cuts 112 may be formed by grooving tool 28 at the sametime that grooves 106 are formed. However, this requires modifyinggrooving machine 10, by, for example, providing that superstructure 22be slidable vertically relative to arrow 32 and suitably cammed to raiseand lower grooving tools 28 at fixed intervals. As edge 114c of board105 is fed between roller 18 and hold-down wheel 66, grooving tools 28may initially be set to cut entirely through the board 105 for thelength of cut 112. Superstructure 22 may slide up in response to acamming device to form grooves 106 and then slide down to form cuts 112in edge 114a of board 105.

In order to make grooves 108a and b, the board 105 is rotated 90 degreesand driven past two grooving tools 28 of grooving machine 10.

Once grooves 106 and 108 and cuts 112 are made, board 105 is foldedalong grooves 106b, c and d edges 114a and 114b are abuted next to eachother and attached to form a box structure with four sides, panels L, M,N and O. Panels H, I, J and K may be folded along groove 108b to formthe box top and panels P, Q, and S may be folded along groove 108b toform the box bottom. The top and/or bottom may be secured with glue orother suitable means. As an example, the top side of panels P and R maybe glued to the bottom side of panels Q and S.

Although FIGS. 5, 6 and 7 depict rectangular structures, it should beunderstood that structures having other shapes and having a differentnumber of sides may be made by varying the number of grooving tools 28and the size of included angle 88.

Generally, the number of grooving tools utilized will directly relate tothe number of sides of structure formed. If the grooving tools are usedto form grooves in the interior of a board and also to bevel the edgesof a board, as illustrated in FIG. 1, the number of grooving tools willbe n+1, where n is the number of sides of the structure to be formed. Ifthe grooving tools 28 are utilized only to form grooves in the interiorof the board, and the edges of the board are not beveled, n-1 groovingtools will be utilized.

The distance between grooving tools will determine the shape of thestructure. For instance, in order to form a structure having n sidesequal in length, the n+1 grooving tools should be provided with an equaldistance between adjacent tools. To obtain a square structure, fiveadjacent grooving tools should be provided with an equal distancebetween them. A rectangular structure is formed by positioning fivegrooving tools such that the distance between the first and secondgrooving tools is equal to the distance between the third and fourthgrooving tools. Also, the distance between the second and third groovingtools is equal to the distance between the fourth and fifth groovingtools.

By changing the size of the included angle 88, the angle of the cornersformed may be varied. Generally, to form a corner having an angle of Xdegrees, the included angle 88 of the grooving tool 28 will be X degreesplus an adjustment factor, between 0 and 5 degrees, inclusive. Theadjustment factor depends upon the thickness d from the bottom of thegroove to the outside surface of the board. In general, if d is verysmall the included angle 88 may approach the angle desired for thecorner being formed. As d becomes thicker, the adjustment in theincluded angle must be made to provide for clearance for the fiberspressed into the inner radius of the fold. Thus, the angle 88 must beincreased. The adjustment does not generally exceed 5 degrees. For astructure having n sides each equal in length, the included angle 88will be (360/n) degrees plus the adjustment factor.

Materials utilized with this invention are generally board materials,such as paper-based boards, paper board, corrugated paperboard orparticle board. However, other types of board-like material, includingfoam board or plaster board are also suitable.

The invention is also especially useful for grooving board materialswhich are generally thicker than those used in the art of box makingfrom paper-based materials. It is particularly useful for grooving boardmaterial of at least 150 points (0.150 inches) and especially formaterials with thicknesses of from 200 points to 300 points, inclusive.By grooving materials of these thicknesses, structures may be formedwhich possess the strength and durability of structures made from moreexpensive materials, such as, plywood or flake board.

In one application of the invention, a rectangular piece of 250 pointparticle board (about 0.250 inches thick) was coated with a decorativevinyl film which simulated a wood grain. The board was grooved with fivegrooving tools in the manner described in FIG. 1. Each grooving tool hadan included angle of 92 degrees. Adjacent grooving tools were spacedequidistant from each other and the first and fifth grooving tools wereadjusted to cut completely through the board and vinyl film and bevelthe edges of the board. The second, third and fourth grooving tools wereadjusted to groove completely through the particle board down to theinner surface of the vinyl film. Thus, the board was hinged on the vinylfilm such that folding the board along the grooves and abutting the twobeveled edges produced four sharp clean corners. The facing surfaces ofthe grooves were glued and the abutting two beveled surfaces wereattached. The precision grooving and folding produced a structuresimulating a wooden cabinet having corners which were strong andaccurately formed.

The terms and expressions employed herein are terms of description andnot limitation. There is no intention to exclude any equivalence of thefeatures shown and described. It is recognized that variousmodifications are possible within the scope of the invention claimed.

I claim:
 1. Apparatus for grooving board material having a first andsecond surface comprising:a grooving tool means having a V-shapedleading cutting edge with a preselected included angle for cutting aV-shaped groove in the first surface of the board material to a depthwhich is a preselected distance from the second surface, said groovingtool means including an elongated member, one end of which is providedwith the V-shaped leading cutting edge; means for producing relativemovement of said grooving tool means and said board material to cut theV-shaped groove in said board material; guide means for inhibitingnonlinear relative movement of said V-shaped leading cutting edge andsaid board material while cutting the V-shaped groove to cause astraight groove to be cut in said board, said guide means including holddown means for maintaining said board material in firm engagement withsaid V-shaped leading cutting edge while cutting said V-shaped groove,said hold down means including a body, a first member pivoted to saidbody, a second roller rotatably affixed to said first member and springloading means for urging said second roller against said board materialto resiliently press the board material against the movement producingmeans; and a superstructure supported over said grooving tool means,said hold down means being affixed to said superstructure and saidgrooving tool means being adjustably mounted on said hold down means toadjust the preselected distance of the V-shaped groove from the secondsurface of the board material.
 2. Apparatus for grooving board materialhaving a first and second surface comprising:a grooving tool meanshaving a V-shaped leading cutting edge with a preselected included anglefor cutting a V-shaped groove in the first surface of said boardmaterial to a depth which is a preselected distance from the secondsurface; means for producing relative movement of said grooving tool andsaid board material to cut the V-shaped groove in said board material;guide means for inhibiting nonlinear relative movement of said V-shapedleading cutting edge and said board material while cutting the V-shapedgroove to cause a straight groove to be cut in said board; said groovingtool means including an elongated member having an upper shank portionand a lower shoe portion, said lower shoe portion extending between theupper shank portion and the V-shaped leading cutting edge and beingprovided with a V-shaped bottom surface adjacent to and extending awayfrom the V-shaped leading cutting edge, said V-shaped cutting edgehaving first and second sides which form the V-shaped leading cuttingedge, the V-shaped bottom surface having third and fourth sidessubstantially coplanar with the first and second sides of the V-shapedleading cutting edge; and p1 said guide means including hold down meansfor maintaining the board material in firm engagement with the V-shapedleading cutting edge while cutting the V-shaped groove, said upper shankportion being adjustably mounted in said hold down means for adjustingthe preselected distance of the V-shaped groove from the second surfaceof the board material.
 3. The apparatus according to claim 2, whereinthe shoe portion of the grooving tool is provided with an inner curvedcontour means between said third and fourth sides for lifting a V-shapedfillet, cut from said board material to form the V-shaped groove, awayfrom said V-shaped groove.
 4. Apparatus for grooving board materialhaving a first and second surface comprising:a grooving tool meanshaving a V-shaped leading cutting edge with a preselected included anglefor cutting a V-shaped groove in the first surface of said boardmaterial to a depth which is a preselected constant distance from thesecond surface; means for producing relative movement of said groovingtool and said board material to cut the V-shaped groove in said boardmaterial; and guide means for inhibiting nonlinear relative movement ofsaid V-shaped leading cutting edge and said board material while cuttingthe V-shaped groove to cause a straight groove to be cut in said board.5. The apparatus according to claim 4, wherein said grooving tool meansincludes an elongated member, one end which is provided with theV-shaped cutting edge having the preselected included angle, and whereinsaid guide means includes hold down means for maintaining said boardmaterial in firm engagement with said leading cutting edge while cuttingsaid V-shaped groove, said elongated member being adjustably mounted onsaid hold-down means to adjust the preselected distance of the V-shapedgroove from the second surface of said board material.
 6. The apparatusaccording to claim 4, wherein said producing means comprises a firstroller.
 7. The apparatus, according to claim 6, further including asupport platform positioned tangentially to said first roller.
 8. Theapparatus, according to claim 5 or 6 wherein said hold-down meansincludes a second roller means for resiliently pressing the boardmaterial against the producing means.
 9. The apparatus, according toclaim 4, wherein said grooving tool means is adjustably mounted on saidguide means for adjusting the preselected distance of the V-shapedgroove cut in the board material from the second surface of said boardmaterial.
 10. The apparatus, according to claim 5, wherein said groovingtool means is provided with a V-shaped bottom surface adjacent theV-shaped leading cutting edge and extending away from said V-shapedleading cutting edge, the V-shaped bottom surface being provided with asubstantially straight lower edge.
 11. The apparatus, according to claim10, wherein the angle formed between the substantially straight loweredge and said groove is at least 0 degrees and not greater than 20degrees.
 12. The apparatus, according to claim 11, wherein said angle isat least 2 degrees and not greater than 10 degrees.
 13. The apparatusaccording to claim 1, wherein said grooving tool means includes a firstgrooving tool means for producing a first groove in said board materialat a first preselected distance from the second surface and a secondgrooving tool means for producing a second groove in said board materialat a second preselected distance from the second surface.
 14. Theapparatus according to claim 13, wherein said first preselected distanceis less than the thickness of said board material.
 15. The apparatusaccording to claim 1, wherein the preselected included angle of saidV-shaped leading cutting edge is at least 90 degrees and not greaterthan 95 degrees.
 16. The apparatus according to claim 12, wherein saidincluded angle is at least 91.5 degrees and not greater than 93.5degrees.
 17. The apparatus according to claim 2, including asuperstructure supported over said grooving tool means, said hold-downmeans being affixed to said superstructure.
 18. The apparatus accordingto claim 14, wherein said grooving tool means is affixed to saidhold-down means.
 19. The apparatus according to claim 15, wherein saidhold-down means includes a second roller means for resiliently pressingthe board material against the producing means.
 20. The apparatusaccording to claim 5, wherein said grooving tool means includes anelongated tool member, one end of which is provided with a V-shapedcutting edge having a preselected angle, and said elongated member isadjustably mounted on said hold-down means to adjust the preselecteddistance of the V-shaped groove from the second surface of said boardmaterial;said producing means including a first roller for advancingsaid board material linearly relative to said grooving tool means toform a linear V-shaped groove in said board material; said hold-downmeans including a second roller means for resiliently pressing the boardmaterial against the first roller; and further including supportingmeans including a platform, positioned tangentially to said firstroller.
 21. The apparatus according to claim 20, wherein the preselectedangle of said V-shaped cutting edge is at least 90 degrees and notgreater than 95 degrees.
 22. The apparatus according to claim 21,wherein said grooving tool means includes means for cutting five linearspaced-apart parallel V-shaped grooves in said board material. 23.Method for grooving a sheet of board material having a first and secondsurface comprising:advancing said sheet relative to a V-shaped leadingcutting edge of a grooving tool, said cutting edge having a preselectedincluded angle; simultaneously, guiding said sheet to prevent nonlinearrelative movement of said leading cutting edge and said sheet of boardmaterial; and cutting a V-shaped groove in the first surface of thesheet of board material at a preselected distance from the secondsurface of the sheet of board material at said sheet advances relativeto said V-shaped leading cutting edge.
 24. The method, according toclaim 23, further including:supporting said sheet on a support; andmaintaining said sheet in firm engagement with said V-shaped leadingedge of said grooving tool as said sheet advances relative to saidV-shaped leading cutting edge.
 25. The method, according to claim 24,wherein said cutting step includes:cutting a plurality of adjacent,substantially straight, spaced and parallel V-shaped interior grooves ina piece of board material, each of the V-shaped grooves having twoopposing faces, a depth less than the thickness of the board material, apreselected first included angle, and being parallel to a first andsecond side of said piece of board material.
 26. The method, accordingto claim 25, further including the step of beveling the first and secondsides of said rectangular piece by cutting an additional V-shaped grooveat a depth substantially equal to the thickness of said piece of boardmaterial, along each of said first and second sides.
 27. The method,according to claim 25 or 26, further including the step of:folding saidpiece of board along each of said plurality of interior grooves suchthat said first and second sides of the piece of board are brought intoabutment and opposing faces of each of said interior grooves are broughtinto abutment to form a structure having a plurality of corners, each ofsaid corners having a second included angle.
 28. The method, accordingto claim 27, further including the step of:fastening the first andsecond sides to form a structure having a number of sides equal to thenumber of interior grooves plus one.
 29. The method, according to claim28, wherein the size of said first included angle is equal to the sizeof the second included angle plus an adjustment factor not greater than5 degrees.
 30. The method, according to claim 29, wherein the number ofsides of said structure is four.
 31. The method, according to claim 30,wherein the second preselected angle is substantially equal to 90degrees.
 32. The method, according to claim 31, wherein the firstincluded angle is between 90 and 95 degrees, inclusive.
 33. The method,according to claim 32, wherein the first included angle is between 91.5and 93.5 degrees, inclusive.
 34. The method, according to claim 25 or26, wherein the thickness of the board material is at least 150 points.35. The method, according to claim 34, wherein the thickness is between200 points and 300 points, inclusive.
 36. A rectangular structure formedby the method of claim
 27. 37. A rectangular structure formed by themethod of claim
 28. 38. The method according to claim 34, wherein theboard material is particle board or chipboard.